Elastic fluid turbine



Filed June 17, 1938 R H 4.117 L m 1% m m t5 0 w e v J m Tme w Patented Mar. 18, 1941 UNITED STATES ELASTIC FLUID TURBINE Walter E. Blowney,

New York Schenectady, N. Y., assignmto General Electric Company,

a corporation of Application June 17, 1938, Serial No. 214,369

2 Claims.

The present invention relates to elastic fluid turbines of the multi-stage type. In these turbines the load distribution among the several stages is non-uniform, especially during low or partial load condition when, for instance, the load across the first stage may be as high as 80% of the total load and the load across all other stages only 20% of the total load. To obtain a better load distribution it is known to supply high pressure steam to the first stage and also to one or several of the intermediate or lower stages, or to bypass elastic fluid from one of the higher stages to one of the lower stages.

The object of my invention is to provide an improved turbine construction of the type above specified whereby elastic fluid is bypassed between a higher turbine stage and a lower stage and thereby better load distribution attained.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

The single figure of the drawing illustrates a turbine arrangement embodying my invention.

The turbine comprises a rotor ill with a plurality of bucket wheels ii, i2, it, t l, i5, etc. secured to and, in the present instance, integrally formed with a shaft. Elastic fluid is conducted to the bucket wheels by means of nozzle diaphragms i6, i1, i8, i9, 20, etc. The -first diaphragm i6 and the first bucket wheel ii form the first stage and the diaphragm 20 and the bucket wheel i5 form the fifth stage. All of the diaphragms are connected to and supporteclon an inner casing 21 which is sealed to the rotor shaft by packings 22 to reduce leakage of elastic fluid from the turbine along the shaft. The inner casing 2i is enclosed within and spaced from an outer casing 23 which is also sealed to the turbine shaft by packings 24. Double casings or shells are desirable in modern high pressure, high temperature elastic fluid turbines to reduce the pressure drop across the individual casing or, from another viewpoint, to make it possible to operate turbines with elastic fluids of high temperatures of the order of 1000 F. and pressures of 1200 lbs. per square inch and more. The space formed between the inner and outer casings may be connected to a lower turbine stage so that, for instance, with an inlet pressure of 1000 lbs. per square inch the inner casing at its inlet end is subjected to such pressure on the inside while the outside of the inner casing is subjected to apressure, let us say, of the order of 500 lbs., thus establishing a maximum pressure drop across the inner casing of only 500 lbs. The same pressure drop then would exist across the outer casing whose outside is subjected to atmospheric pressure. The same applies to the tem- 5 perature drops across the two shells of a double casing turbine.

In the present arrangement the outer casing 23 forms a valve chest 25 with an inlet opening 26 for accommodating a movable valve member 10 2! to control the flow of elastic fluid to the inlet of the turbine. The channel for conducting elastic fluid from the valve chest 25 to the diaphragm or nozzle blade it of the first stage includes a sleeve 28 seated on-and secured to the outer cas- 15 ing and projecting into a channel 29 formed by the inner casing. The sleeve 28 is sealed to the inner casing by a floating packing arrangement 30 reducing leakage of elastic fluid from the inlet into the space between the two casings and permitting relative expansion between them without setting up excessive strains and stresses. Elastic fluid supplied to the turbine first passes through the first stage formed by the nozzle blade i6 and the bucket wheel ii and then successively 25 through the succeeding lower stages. A part of the fluid discharged from the first stage, that is, from the bucket wheel ii, however, is conducted through a bypass 3! to a lower stage to reduce the non-uniformity'of loading of the several so stages during partial load condition. The bypass in accordance with my invention has an outer wall 32 and an inner wall defined by a portion of the inner turbine casing 21. In the arrangement shown in the drawing the walls of the bypass are integrally formed with the inner casing 2i and the bypass is arranged to bypass fluid from the outlet of the first stage to the inlet of the fifth stage, that is, the diaphragm 20. The flow of fluid through the bypass 3| is con trolled by a valve 33 in the bypass. The valve 33 has a stem 34 connected by a coupling 35 to a connecting rod 36. The stem 34 is arranged slidably in a packing 31 provided in a flanged member 3Q seated on and secured "to the wall 32 of the channel 3|. The connecting rod 36 is surrounded by a packing sleeve 39 arranged in a flanged member 40 which latter is seated on and secured to the outer casing 23. The coupling 35 permits slight misalignment between the stem 3 and the connecting rod 36. The valve member 33 when closed engages a valve seat 41 formed by a sleeve 42 secured in an opening of the inner casing 2|.

During operation the valve 21 is opened to B5 start the turbine. All 01 the elastic fluid then flows Irom the first stage through the succeeding stages. After the turbine load has reached a certain value the valve 33 is opened to bypass a part of the elastic fluid discharged from the bucket wheel ll of the first stage to the diaphragm 20 of the fifth stage. The bypassing at light load, as pointed out above, causes more uniform distribution of the' load and consequently reduces the maximum stresses particularly on the first stage.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. Multi-stage double shell elastic fluid turbine comprising an inner casing, a rotor forming a plurality of stages and having a shaft sealed to the inner casing, an outer casing surrounding and spaced from the inner casing and sealed to the rotor shaft, means for conducting elastic fluid to the first stage comprising a channel formed partly in the outer and partly in the inner casing. a valve for controlling the flow of fluid through the channel, another channel formed in the space between the two casings to constitute a bypass for conducting elastic fluid discharged from a higher stage to a lower stage, and valve means in the other channel for controlling the flow of elastic fluid through the other channel to control the load distribution among the several turbine stages at a given total load.

2. Multi-stage double shell elastic fluid turbine comprising an inner casing, a rotor having a shaft and forming a plurality of stages disposed within the inner casing, an outer casing surrounding the inner casing and spaced therefrom, means including an inlet valve for conducting and controlling the flow of elastic fluid to the first stage, a channel between the inner and outer casings integrally formed with the inner casing for bypassing a part of the elastic fluid discharged from the first stage with regard to an intermediate stage, and a valve in the channel for controlling the flow of fluid through the channel to cause uniform distribution of the load among the stages at a given total load.

WALTER E. BLOWNEY. 

